Hunkered down in your seat during “The Last House on the Left” back in 1972, you probably wouldn’t have believed that four decades later the carnage unfolding before your eyes would be considered historical.

After all, it was only a movie ... only a movie ... only a movie.

That catchy tag line wasn’t what made the disturbing horror film significant. As David Konow explains in “Reel Terror,” the movie’s primary contribution to the genre was boosting the careers of Wes Craven (later the director of “A Nightmare on Elm Street”) and Sean Cunningham (later the director of “Friday the 13th”). Plus, it gave new meaning to the word “vile.”

Mainstream moviegoers are better acquainted with horror classics such as “Psycho,” “The Exorcist,” “Jaws” and “Halloween,” all of which get their due in Konow’s overview. But his narrative thrives on the details of many other high points of horror — or low points, depending on how you look at it. Examining the genre over time suggests that:

•Horror has been looked down on from the beginning. Even after the success of “Dracula” and “Frankenstein” in the 1930s, movie studio Universal wanted to get out of the monster business. For established directors like William Friedkin (”The Exorcist”) and Stanley Kubrick (”The Shining”) making a horror movie was akin to slumming.

•Major influences can come from unexpected places. The fan magazine Famous Monsters of Filmland and EC Comics inspired readers to become writers and filmmakers. Director George Romero’s low-budget “Night of the Living Dead” (1968) was the midnight movie that launched a thousand zombies.

•Filmmakers should beware of success in an unappreciated genre. Horror hits have pigeonholed people like Romero, Craven and Tobe Hooper of “The Texas Chain Saw Massacre” fame, limiting their opportunities to direct different kinds of movies. On the other hand, each has secured a place in cinema history.

For a book that claims to span a century, Konow gives short shrift to the first five decades or so. Significant 1930s films like “Freaks” and “Dr. Jekyll and Mr. Hyde” are all but ignored. The frights of the atomic age (”Godzilla”) and the space age (”The Thing From Another World,” “The Blob”) and the youth-oriented horror movies of the 1950s (“I Was a Teenage Werewolf”) are passed over in favor of more recent films.

Konow does yeoman’s work when it comes to collecting facts from previously published material and presenting quotes from fresh interviews. Yet, at times, he assumes a level of knowledge beyond what many potential readers will possess.

Moreover, Konow falls short when it comes to providing the analysis that’s necessary to pull together all the pieces and make the subject really come alive. That leaves “Reel Terror” less animated than it should be.

Douglass K. Daniel is the author of “Tough as Nails: The Life and Films of Richard Brooks” (University of Wisconsin Press).